ASHBURN, Va. -- The Washington Football Team, with a roster already depleted by COVID-19, added starting quarterback Taylor Heinicke to the reserve list for players affected by the virus, sources told ESPN's Adam Schefter and Field Yates on Friday.

Heinicke is the 22nd Washington player on the list, leaving the team without its top two quarterbacks for Sunday's game at the Philadelphia Eagles. Heinicke's backup, Kyle Allen, was placed on the reserve list Wednesday, but there is a chance he could play Sunday depending on the results of further testing.

Heinicke, who has been vaccinated, would likely be a longshot to return. A source told Schefter that Washington is unlikely to name a starter until Sunday.

Washington signed quarterback Garrett Gilbert off the New England Patriots' practice squad as insurance, sources told Schefter and Yates, adding that Gilbert could be called on to start Sunday's game.

Gilbert has deep ties to the Washington coaching staff. He was on the Raiders roster for two years when Washington defensive coordinator Jack Del Rio was the head coach and played for coach Ron Rivera and offensive coordinator Scott Turner in Carolina in 2017-18.

Washington (6-7) plays at Philadelphia (6-7) on Sunday in a game pivotal to both teams' playoff chances. Washington owns the seventh and final spot in the NFC with four games remaining.

Earlier this week, Washington signed Jordan Ta'amu, who started ahead of Heinicke for the St. Louis Battlehawks of the XFL in 2020. Washington also has Kyle Shurmur, who has been on the practice squad since Sept. 13.

Washington's roster has been ravaged by the coronavirus this week, though almost all players on the reserve list have been vaccinated and multiple players reported no symptoms.

Compounding the situation: Wide receiver Terry McLaurin and third-down back J.D. McKissic are in the concussion protocol and might not play. Wide receiver Curtis Samuel (hamstring) has not practiced this week, and backup wide receiver Cam Sims, who would replace McLaurin, is on the reserve/COVID-19 list.

As of now, Washington has four of its original five starting offensive linemen, running back Antonio Gibson and two of its original top three tight ends. Defensively, Washington is without six of its top seven linemen and two starting defensive backs.